Best route painting barreled action

What’s your budget and how rough are you on your toys? You can go as simple as camo wrap or Scotchbrite and Krylon or a dip if you like. Cerakote looks good and takes a beating hence its popular.
 
Duracoat. I sprayed my AI, was easy and dried fast.

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Aervoe paint is a good cheap option. It's more durable than Krylon or others. It comes in several colors too. Just give it a few days to dry completely.
 
I’m using Aervo for a stock and AR furniture but I plan on using Alumahyde II on a Howa action. I used it on a Savage before and it seemed to be more durable than anything else from a can. It takes 2 weeks to cure, though, and the nozzles clog. I kept the nozzle soaking in acetone to keep it clear.
 
Alumahyde II when done right is tough as nails. Prep the surface, keep the cans mixed, buy extra nozzles, be patient.....DO NOT TOUCH IT...lol

I would always hang the part up in a closet and pretend it didn’t exist for 2 weeks. I also had good results with application by heating the can in a hot water bath and heating the parts a little with a hair dryer.